Does an individual that entered Mexico on an FMT (tourist visa) and then applied and received an FM3 have to go to the border to re-register the vehicle under the FM3?
No. As long as your migratory status (other than an FMT) is current the vehicle remains legal even if the permit is expired.

When an individual finishes one 5 year FM3, then receives a new book renewal, does this person need to return to the border to renew the permit?
No. The same rules apply; just keep your migratory status current. These same rules apply to FM2 holders as well. This is all stated in Article 106 of Mexico's Customs Law.

Can an individual that has been granted Inmigrado status in Mexico drive a foreign plated vehicle?
No. They must take their foreign plated vehicle out of Mexico.

If a road block is encountered, can my auto be seized for some reason?
The only authority allowed to do this is Aduana (Customs), and Administracion Local de Auditoria Fiscal Federal. No other authority, which means the Traffic Police, City Police, the Federal police, or the Military, has the right to seize foreign plated vehicles . The only way these entities can do anything with foreign plated vehicles is with permission from Aduana or Administracion Local de Auditoria Fiscal Federal. And this authorization would only be given to go after an individual.

With this said, know your rights, these other authorities cannot even ask for the vehcile importation papers as it is not within their responsibility. If you are threatened by these other authorities about the status of your vehicle, or even your migratory status, record as much information about this authority as possible. Name, badge number, date, officer's vehicle type, officer's vehicle license and unit number, etc. Aduana is very clear on this and wants everyone possible to report such issues to the proper authorities. Most of these authorities will back off once they realize that you know your rights and start recording this information about them.

What documents should I have in the vehicle with me?
Aduana has indicated the following COPIES of documents should be in a foreign plated car at all times:

Proof of your migratory status - copy of your passport, your migratory status form with the current renewal date

Never leave original documents in a vehicle in case the car is stolen. You will need those originals if the vehicle is ever stolen.
Temporary Vehicle Importation Regulations From Secretaria de Hacienda Y Credito Publico

ARTICLE 106 CUSTOMS LAW

ARTICLE 106. Temporary importation is understood as the entry of merchandises into the country, which will remain in it for a limited period of time and for a specific purpose, so long as they are returned abroad in the same condition. The former applies for the following terms:

PART IV. For the term of his or her migratory status, including extensions, in the following cases:

a) Vehicles owned by tourists, visitors, local visitors and distinguished visitors, students, and immigrants who are tenants, whenever said vehicles are their own, excepting tourists and local visitors. When the vehicles are not their own, requirements established within the regulations must be met. Such vehicles may be driven within the national territory by a foreigner --the importer-holding one of the migratory status referred to in this paragraph, by his or her spouse, parents or descendants, even when the latter are not foreigners: and by a Mexican as long as one of the persons authorized to drive the vehicle travels with him or her in the car. Vehicles referred to in this section must meet the requirements pointed out in the regulations.

b) Used household furniture and wares owned by the visitors, distinguished visitors, students and immigrants, so long as they meet the requirements pointed out in the regulations. This information is provided courtesy of Adriana Perez Flores, Attorney at Law, Ajijic Legal and Immigration Services, Ajijic, Jalisco C.P. 45920 Mexico. For more info Email info@AjijicLaw.com or visit their website www.ajijiclaw.com